Spray nozzles have been developed that utilize a central tube to carry a liquid and an outer tube, usually concentric with the inner tube, to carry a gas that assists with nebulization of the liquid. The respective outlets of the central tube and the outer tube are positioned relative to each other such that the flow of liquid is merged into the surrounding flow of gas, whereby the stream of liquid through interaction with the stream of gas is broken up and converted to a spray of droplets of the liquid carried by the flow of gas, i.e., an aerosol is created. The resulting spray, or aerosol, may be utilized for a wide range of purposes depending on the application. Of particular interest is the generation of a sample spray, i.e., a spray that contains droplets carrying sample material for which some type of analysis is sought. A sample spray may, for example, provide the sample material for implementing mass spectrometry (MS) or optical emission spectrometry (OES).
One type of sample spraying device is known as a gas dynamic virtual nozzle (GDVN). A GVDN includes a central tube that emits a stream of liquid sample and is surrounded by an outer tube. A flow of gas is established through the annular passage formed between the central tube and the outer tube. The outer tube has a section that converges down to an exit orifice in front of, and at an axial distance from, the exit opening of the central tube. By this configuration, the stream of liquid sample exits the central tube and into a space in which the liquid sample encounters the gas supplied through the annular passage. The interaction between the gas and the liquid sample causes the liquid sample to break up into droplets, with the result that a sample spray emerges from the exit orifice of the outer tube, which serves at the nozzle exit of the GDVN.
Current designs for GDVNs and other sample sprayers are limited by the fact that they either do not provide a way to adjust the position of the central tube relative to the exit orifice or do not provide a way to adjust the position of the central tube while the sample sprayer is operating, i.e., while the gas and liquid flows through the sample sprayer are active. Thus, in current designs optimization of the sample spray is difficult to achieve.
Therefore, there is a need for improvements in the design of sample sprayers.